Aircraft fuselage structures made from metal or, more recently, also from composite materials, are manufactured by joining several fuselage sections, thereby creating transverse seams, in order to simplify the production process. The fuselage sections themselves are formed from at least two shell segments, though more preferably from four shell segments, which are joined by creating at least two longitudinal seams on their periphery. The shell segments are formed from at least one piece of bent sheet metal, which on its inner side is riveted to several frame segments and further reinforcement profiles in such a manner as to support structural loads. The pieces of sheet metal serving as a covering for the frame segments constitute the future outer skin of the aircraft fuselage cabin.
The join of the shell segments has to meet a multitude of static requirements. On the one hand, the join should possess the same structural load bearing capacity as the shell segments at the same life expectancy, and, on the other hand, the join should not lead to an increase in overall weight. Further the join should exhibit the same error tolerance as the shell segments, and easy visual inspection during regular maintenance work should be possible.
In order to fulfill these requirements, conventional frame couplings to date are carried out as single shear butt joints. An advantage of this is that the joined components can be inspected visually from one side, but it also has the disadvantage that a greater number of connecting elements, in particular rivets, is necessary. Moreover, this uneven coupling technique presents the disadvantage that the inevitable geometric offset of the frame coupling and both frame segments entails undesirable offset moments, in particular about a y-axis. These additional moments are introduced into the fuselage cabin structure, and have to be taken into account statically by means of structural elements having larger dimensions, and, as a result, thus entail an increase in weight.
Therefore, it is an object of the present invention to provide a coupling of a new type for joining frame segments within a fuselage cabin structure of an aircraft, which allows moment-free linking of the arc-shaped frame segments to be joined.
This object is achieved by a frame coupling comprising the features set out in claim 1.
Due to at least one side plate being arranged in an area of one side of the web, and at least one counter plate being provided in at least a part of an area of an opposing side of the web, the frame coupling according to the invention exhibits a high degree of symmetry. Because of the connecting plates being provided symmetrically on both sides against the webs of the frame segment profiles, the generation of load-increasing moments in the region of the frame coupling is avoided. In the area of the header flanges of the frame segments, the coupling again is arranged in a single-shear configuration, so that in this area a defined weak point of the coupling is provided, and so that additionally, it is ensured that any secondary damages, such as corrosion and/or signs of fatigue, for example, can be discovered with certainty while the effort necessary for inspection remains unchanged.
In an advantageous embodiment of the coupling, both frame segments are connected through a butt joint, with a frame gap being created thereby.
Thereby, in the process of joining both frame segments by means of the coupling, compensation of tolerances is possible in a simple manner.
According to another advantageous embodiment, the at least one side plate, both frame segments, and the at least one counter plate are connected by means of a multitude of connecting elements, in particular by means of several arrangements of rivets formed by the rivets being disposed in a matrix-like manner.
Owing to the use of conventional rivets as connecting elements, jointing technology widely used in aircraft construction can be made further use of without modifications. Furthermore, the matrix-like arrangement of the connecting elements allows to transmit high forces and moments.
In still another advantageous embodiment, at least one side plate comprises an L-shaped cross-sectional geometry. In this way, the static load-bearing capacity of the coupling is improved.
In still another advantageous embodiment of the frame coupling, the at least one side plate is connected, in particular riveted, to the header flange of the web. This allows to further increase the load-bearing capacity of the frame coupling according to the invention.
Further advantageous embodiments of the coupling are set out in the claims.
In the figures, like reference numbers denote like structural elements.